1. Field of the Invention
The present invention relates to a process for detecting a phenomenon that interferes with visibility and a detection device allowing this process to be implemented.
It will be used in particular in the sphere of motor vehicles.
2. Description of the Related Art
In the case of motor vehicle applications, processes are already known under the state of the art, whereby the presence of a solid obstacle such as a vehicle following closely behind can be observed and a warning can be given if this vehicle gets too close. Such systems work for example on the basis of a distance sensor. In the event of such an obstacle being present and provided that the rear lights are switched on, on a wet road (regardless of whether it is actually raining or not), the visibility of the lights can be affected by a visibility interference such as spray of water produced by the rear wheels of the vehicle or the driver of the vehicle behind; this can be the cause of concern for the driver following and also for the driver being followed. However, such processes do not enable a visibility interference phenomenon to be detected.
Such detection devices are also known. For example, EP 1 715 456, which is equivalent to U.S. Patent Publication 2007/0031006, which is incorporated herein by reference and made a part hereof, describes a process for detecting evening fog along a road in front of a vehicle, comprising a system for illuminating the roadway with the vehicle's headlights. Such systems work on the basis of capturing a series of images of the roadway, extracting a halo of light from these images created by the headlights, comparing this with the nearest elliptical curve and deducing the presence or the absence of fog.
The document EP 1 498 721 describes a fog detection process, comprising a numerical camera, which scans the environment around the vehicle and an imaging system, which compares the luminosity of each pixel of the camera to a predetermined value and then deduces the presence of fog if the luminosity of any of the pixels is lower than the said predetermined value.
The document EP 1 298 481, which is equivalent to U.S. Pat. No. 6,803,574, which is incorporated herein by reference and made a part hereof, describes a night vision device, comprising an infra-red emitter, a detector and a display device. The emitter comprises one or more pulse emitting diodes, which are operated by a driver, which operates simultaneously the detector or a camera. This document does not cover fog applications.
The document EP 1 553 429, which is equivalent to U.S. Pat. No. 7,350,945, which is incorporated herein by reference and made a part hereof, describes a system for detecting traffic conditions on a roadway (both weather conditions and the detection of obstacles), which is mounted on a motor vehicle and comprises at least one light projector having a first light source emitting a visible beam of light and at least one source of modulatable light, in particular at a high frequency, emitting a beam of infra-red light along the road ahead and at least one camera able to capture images of the road ahead.
The document “Fog lamp automation with visibility sensor, the next step of lighting automation”, by J. Lelevé et al., appearing in the VDI Report No. 1907, 2005, describes a passive fog detection system, based on cameras and image processing but without the emission of a light beam.
The document “OptiVeo: A Vision-Based Platform for Driving Assistance”, by P. Reilhac et al., from the SAE World Congress, 2006, describes a passive fog detection system, on the basis of cameras and image processing, but not including the emission of a light beam.
The document EP 1 790 541, which is equivalent to U.S. Patent Publication 2007/01153357, which is incorporated herein by reference and made a part hereof, describes a device for detecting dirty marks on the windscreen of a motor vehicle, which uses two cameras and an image processing system.
The document FR 2 847 367 describes a passive process and device to determine the distance visibility in the present of an element interfering with visibility such as fog, although this does not comprise any emission of a light beam.